var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";  
//将Ansi编码的字符串进行Base64编码  
function encode64(input) {  
    var output = "";  
    var chr1, chr2, chr3 = "";  
    var enc1, enc2, enc3, enc4 = "";  
    var i = 0;  
    do {  
        chr1 = input.charCodeAt(i++);  
        chr2 = input.charCodeAt(i++);  
        chr3 = input.charCodeAt(i++);  
        enc1 = chr1 >> 2;  
        enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);  
        enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);  
        enc4 = chr3 & 63;  
        if (isNaN(chr2)) {  
            enc3 = enc4 = 64;  
        } else if (isNaN(chr3)) {  
            enc4 = 64;  
        }  
        output = output + keyStr.charAt(enc1) + keyStr.charAt(enc2) + keyStr.charAt(enc3) + keyStr.charAt(enc4);  
        chr1 = chr2 = chr3 = "";  
        enc1 = enc2 = enc3 = enc4 = "";  
    } while (i < input.length);  
    return output;  
}  
//将Base64编码字符串转换成Ansi编码的字符串  
function decode64(input) {  
    var output = "";  
    var chr1, chr2, chr3 = "";  
    var enc1, enc2, enc3, enc4 = "";  
    var i = 0;  
    if (input.length % 4 != 0) {  
        return "";  
    }  
    var base64test = /[^A-Za-z0-9\+\/\=]/g;  
    if (base64test.exec(input)) {  
        return "";  
    }  
    do {  
        enc1 = keyStr.indexOf(input.charAt(i++));  
        enc2 = keyStr.indexOf(input.charAt(i++));  
        enc3 = keyStr.indexOf(input.charAt(i++));  
        enc4 = keyStr.indexOf(input.charAt(i++));  
        chr1 = (enc1 << 2) | (enc2 >> 4);  
        chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);  
        chr3 = ((enc3 & 3) << 6) | enc4;  
        output = output + String.fromCharCode(chr1);  
        if (enc3 != 64) {  
            output += String.fromCharCode(chr2);  
        }  
        if (enc4 != 64) {  
            output += String.fromCharCode(chr3);  
        }  
        chr1 = chr2 = chr3 = "";  
        enc1 = enc2 = enc3 = enc4 = "";  
    } while (i < input.length);  
    return output;  
}  
  
function utf16to8(str) {  
    var out, i, len, c;  
    out = "";  
    len = str.length;  
    for(i = 0; i < len; i++) {  
        c = str.charCodeAt(i);  
    if ((c >= 0x0001) && (c <= 0x007F)) {  
        out += str.charAt(i);  
    } else if (c > 0x07FF) {  
        out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));  
        out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));  
        out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));  
    } else {  
        out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));  
        out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));  
    }  
    }  
    return out;  
}  
  
function utf8to16(str) {  
    var out, i, len, c;  
    var char2, char3;  
    out = "";  
    len = str.length;  
    i = 0;  
    while(i < len) {  
        c = str.charCodeAt(i++);  
        switch(c >> 4) {  
            case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:  
                // 0xxxxxxx  
                out += str.charAt(i-1);  
                break;  
            case 12: case 13:  
                // 110x xxxx 10xx xxxx  
                char2 = str.charCodeAt(i++);  
                out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));  
                break;  
            case 14:  
                // 1110 xxxx 10xx xxxx 10xx xxxx  
                char2 = str.charCodeAt(i++);  
                char3 = str.charCodeAt(i++);  
                out += String.fromCharCode(((c & 0x0F) << 12) |  
                ((char2 & 0x3F) << 6) |  
                ((char3 & 0x3F) << 0));  
                break;  
        }  
    }  
    return out;  
}  
  